Paper/Archive/CVE-2026-39831

CVE-2026-39831

golang.org/x/crypto golang.org/x/crypto/ssh — Invoking bypass of FIDO/U2F security keys physical interaction in golang.org/x/crypto/ssh

EPSS 0.5%CVSS 9.1

critical.is priorityof 100

CVSS 9.1 (ADP)9.1 / 10 × 3027.3 Not in CISA KEV+300.0 EPSS percentile 41.3.413 × 208.3 No public exploit+100.0 SSVC exploitation: none+100.0

Description · from the CVE record

The Verify() method for FIDO/U2F security key types ([email protected], [email protected]) did not check the User Presence flag. Signatures generated without physical touch were accepted, allowing unattended use of a hardware security key. To restore the previous behavior, return a "no-touch-required" extension in Permissions.Extensions from PublicKeyCallback.

Affected

ProductAffectedFixed inSource

golang.org/x/crypto/ssh< 0.52.00.52.0CNA

Scores by source

CISA ADP9.1CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

CISA ADPSSVCExploitation: none · Automatable: yes · Technical impact: total

References

refgo.dev/issue/79566 refgroups.google.com/g/golang-announce/c/a082jnz-LvI refgo.dev/cl/781662 refpkg.go.dev/vuln/GO-2026-5019